Broadband etching-free metal grating couplers embedded in titanium dioxide waveguides

Metal grating couplers embedded into a titanium dioxide layer are proposed. A coupling efficiency better than 20% is experimentally demonstrated with a 3 dB bandwidth of 86 nm which is in agreement with simulation results. This allowed us to perform error-free transmissions of 10 Gbit/s wavelength multiplexed signals in the C-band.